1. Field of the Invention
The current disclosure relates to circuit design, and, in particular, to circuit design of a decision feedback equalizer.
2. Description of the Related Art
In high frequency application, for example, systems with Gigahertz frequency, the input buffer or the DIVW (Data-Input-Valid-Window) is not able to recognize the extremely small amplitude of the input data, since the o input data has extremely high frequency. The input data with extremely high frequency also has an extremely short period. Therefore, a high frequency system requires implementation of a decision feedback equalizer to enhance the capability of recognizing the amplitude of the input data.
FIG. 1 schematically illustrates a conventional decision feedback equalizer. As shown in FIG. 1, the decision feedback equalizer 100 comprises a plurality of amplifying latch modules 102. Each of the amplifying latch modules 102 comprises an amplifier 104 and a latch 106. The latch 106 is configured to latch an output signal of the amplifier circuit 104. An output signal of the latch 106 of the amplifying latch module 102 is an output signal of the decision feedback equalizer 100. The amplifier circuit 104 is configured to provide an amplifying signal of the input signal. Moreover, the amplifier circuit 104 also takes the output signal of a latch 106 in the previous stage as a feedback signal, and uses the output signal to adjust the driving capability. The output signal is also the feedback signal.
A voltage upper limit of an input signal going into the decision feedback equalizer 100 is a voltage upper limit of an external voltage. A voltage upper limit of the feedback signal is a voltage upper limit of an inner voltage of the decision feedback equalizer 100. However, the voltage of the input signal is higher or lower than the voltage of the feedback signal in different applications. If the voltage of the input signal is much higher than the voltage of the feedback signal, the feedback effect is not obvious. In contrast, if the voltage of the input signal is much lower than the voltage of the feedback signal, the output signal will be the feedback signal. This does not meet the requirements of current circuit design.
Thus, there is a need for a decision feedback equalizer having adjusted feedback capability to improve the shortcoming of the conventional design.